The aerospace giant has been under scrutiny since the March 10 crash of an Ethiopian Airlines jet, which came on the heels of an October Lion Air crash. Together the crashes claimed 346 lives.

Boeing said it is 'making steady progress' on a fix to the jet's anti-stall system that is thought to be a factor in both accidents.

The company has conducted more than 135 test flights of the fix and is working with global regulators and airlines, it said in a news release.

'Across the company, we are focused on safety, returning the 737 MAX to service, and earning and re-earning the trust and confidence of customers, regulators and the flying public,' said Chief Executive Dennis Muilenburg in a press release.

The company announced earlier this month it was cutting monthly production of the 737 by about 20 percent.